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The Great Molasses Flood of 1919: Boston’s Sweetest Disaster

At about 12:30 p.m. on January 15, 1919, residents of Boston’s North End heard a sound like machine-gun fire. Steel rivets the size of fists tore loose from a 50-foot tank on Commercial Street and flew through the air. Then came the wave: 2.3 million gallons of dark molasses, more than 25 feet high, racing through the streets at 35 miles per hour. The Great Molasses Flood had begun. Within minutes, 21 people were dead and 150 more were injured.

Key Facts at a Glance

The Great Molasses Flood occurred on January 15, 1919, at approximately 12:30 p.m. in Boston’s North End, when a 50-foot steel tank operated by the Purity Distilling Company ruptured at 529 Commercial Street.
The collapsed tank released about 2.3 million gallons of molasses in a wave roughly 25 feet high traveling at 35 miles per hour, killing 21 people and injuring approximately 150.
Purity Distilling was a subsidiary of United States Industrial Alcohol (USIA), which fermented molasses to manufacture alcohol for World War I munitions and post-war rum.
Court-appointed auditor Colonel Hugh W. Ogden ruled in April 1925, after 341 days of testimony from roughly 3,000 witnesses, that USIA’s negligent tank construction caused the disaster.
A 2016 Harvard University study led by Nicole Sharp, Jordan Kennedy, and Shmuel Rubinstein concluded that cold January air thickened the molasses as it spread, suffocating victims who might otherwise have survived.

What Happened During the Great Molasses Flood?

January 15, 1919, broke unseasonably warm in Boston. Midday temperatures climbed above 40°F after days of bitter cold. On Commercial Street, dockworkers loaded freight cars, three children gathered firewood beside the Purity Distilling tank, and firefighters at Engine 31 ate lunch over a card game. The hulking gray tank had loomed over the neighborhood since 1915.

At 12:30 p.m., the tank announced its failure. Witnesses described a low rumble, then a metallic ripping sound, then the rapid-fire popping of rivets shooting outward like shrapnel. Steel plates peeled open. A wall of molasses surged into Commercial Street, lifting freight wagons, snapping telegraph poles, and flinging a five-ton truck into the side of a building. The wave knocked Engine 31’s firehouse off its foundation. The elevated railway’s steel supports buckled, sending a passenger train derailing onto the platform below.

The Boston Globe later reported that buildings “cringe up as though they were made of pasteboard” as the wave hit them. Survivors lay trapped in waist-deep syrup that hardened around them as the air cooled.

Police, firefighters, and roughly 100 sailors from the USS Nantucket reached the scene within minutes. Rescuers waded into thigh-deep molasses to pull survivors from the wreckage. Cleanup took weeks: city workers eventually realized that saltwater pumped from Boston Harbor was the only liquid that broke the molasses down. Boston Harbor itself ran brown for nearly six months.

Disaster Stat	Figure
Date and time	January 15, 1919, ~12:30 p.m.
Volume of molasses released	2.3 million U.S. gallons (≈8.7 million liters)
Wave height	15–40 feet (varied by location)
Wave speed	≈35 mph (15 m/s)
Deaths / injuries	21 / ~150
Cleanup labor	~87,000 worker hours

Why Did the Purity Distilling Tank Fail?

USIA built the tank in 1915 to cash in on World War I demand for industrial alcohol, used to manufacture cordite, a smokeless gunpowder. Production schedules trumped safety from the start. Arthur P. Jell, USIA’s assistant treasurer, oversaw the construction despite having no engineering background. He could not read a blueprint. Jell hired Hammond Iron Works to build the tank, never consulted an architect or engineer for inspection, and tested the finished structure by filling it with just six inches of water rather than full saltwater pressure-testing.

The tank leaked from its first filling. Steel plates were too thin and contained too little manganese, making them brittle in cold weather. A maintenance worker named Isaac Gonzales repeatedly warned Jell about leaks, dropped rust flakes onto his desk as evidence, and developed nightmares so vivid that he ran through Boston’s streets in the summer of 1918 to confirm the tank was still standing. USIA’s response, in August 1918, was to repaint the tank brown to camouflage the seeping molasses.

Children in the North End scooped up molasses with sticks to make impromptu candy. Local caulkers John Urquhart and Patrick Kenneally were brought in twice to seal the joints; Urquhart’s last attempt was on December 20, 1918 — less than four weeks before the rupture.

On January 13, 1919, USIA pumped a fresh 600,000-gallon shipment of warm Caribbean molasses into the tank, bringing it to near-capacity. Two days later, the tank failed.

Who Were the Victims of the Boston Molasses Disaster?

The dead included longshoremen, city workers, teamsters, firefighters, and three children. Among the youngest: ten-year-old Maria di Stasio, killed instantly while gathering firewood, and her ten-year-old neighbor Pasquale Iantosca, struck by a railroad freight car the wave had hurled across the street. Maria’s brother Antonio, age eight, survived with a serious head injury after being flung against a lamppost.

The most agonizing death was George Layhe, a firefighter trapped in an 18-inch crawlspace beneath the collapsed Engine 31 firehouse. Layhe held his head above the rising molasses for roughly four hours before suffocating. Five Boston Public Works Department employees died at their stable on the wharf, alongside more than a dozen city horses. Many bodies were so glazed and disfigured by the sticky residue that identification took days; the last victim, Cesare Nicolo, was not recovered from Boston Harbor until May 12, 1919.

Most of the dead were Italian and Irish immigrants, members of the working-class neighborhood that had absorbed the tank’s risks for four years.

The Six-Year Lawsuit That Reshaped American Engineering

More than 125 plaintiffs filed claims against USIA. The Massachusetts Superior Court consolidated them under Dorr v. United States Industrial Alcohol Co., named for Dudley H. Dorr, a Commercial Street property owner and trustee for the plaintiffs. Dorr’s law firm — newly founded in 1918 with Richard Hale as Hale & Dorr — would later grow into one of Boston’s most prominent legal practices.

USIA’s lead attorney, Charles F. Choate Jr., built the company’s defense around a sabotage theory. He argued that Italian anarchists, then a focus of national anxiety during the first Red Scare, had bombed the tank. The defense leaned on real anarchist activity in Boston and on widespread anti-Italian prejudice. Plaintiffs’ attorney Damon Hall countered with structural engineering experts, MIT Professor C.M. Spofford’s site survey, and the testimony of caulkers, sailors, and Isaac Gonzales himself.

Hearings ran 341 days across three years. The Massachusetts Superior Court appointed Colonel Hugh W. Ogden, a respected attorney and World War I veteran, as auditor. After reviewing roughly 25,000 pages of testimony from 3,000 witnesses, Ogden filed his decision in April 1925.

Ogden rejected the anarchist theory completely. He found USIA fully liable: the tank had been rushed, never properly tested, and built by personnel unable to read engineering plans. Historian Stephen Puleo, whose 2003 book Dark Tide remains the standard account, described Ogden as “grounded in a sense of fairness and justice”. USIA was ordered to pay roughly $1 million in damages — equivalent to more than $17 million today — though Puleo’s archival research suggests post-ruling settlements pushed the total closer to $7 million.

The ruling helped trigger a wave of reform. Massachusetts and other states soon required licensed engineers and architects to sign and seal construction plans for major structures. Modern building permit and inspection regimes trace much of their origin to the molasses case.

What Most Sources Get Wrong About the Great Molasses Flood

Popular accounts describe the flood as a freak accident: a warm shipment plus a sudden cold snap caused a one-in-a-million rupture. The 2016 Harvard fluid-dynamics study by Nicole Sharp, Jordan Kennedy, and Shmuel Rubinstein, presented at the American Physical Society’s Division of Fluid Dynamics meeting in Portland that November, complicates that story in two important ways.

First, the cold made the disaster more deadly, not less. Molasses is a non-Newtonian fluid, roughly 1.5 times denser than water with about 4,000 times the viscosity. Once the warm molasses hit Boston’s January air, it cooled rapidly and thickened, hardening around victims like quicksand. Sharp’s team concluded that a summer flood would likely have killed far fewer people. Second, the warm-shipment narrative obscures four years of negligence: USIA had been warned repeatedly about leaks, ignored Gonzales, declined to involve any engineer, and chose camouflage over repair. The flood was predictable. The cold was the multiplier, not the cause.

Why the Great Molasses Flood Still Matters

For decades after the disaster, North End residents claimed they could still smell molasses on warm summer days. The site of the tank is now Langone Park and Puopolo Park, where a small Bostonian Society plaque commemorates the dead. The case marks a turning point in American industrial accountability — the moment when courts began holding corporations responsible for engineering choices that endangered the public, and when permitting and inspection moved from optional to mandatory. Every signed-and-sealed blueprint owes something to Hugh Ogden’s verdict.

Frequently Asked Questions

How fast did the Great Molasses Flood travel?

The wave moved at approximately 35 miles per hour (15 meters per second) at peak speed. A 2016 Harvard study confirmed contemporary accounts, finding that the warm molasses initially flowed quickly because of shear-thinning, then slowed and thickened as it cooled. The combination of speed at impact and rapid cooling afterward explains both the destructive force and the high death toll.

Did the molasses smell linger in Boston for years?

Yes. Boston Harbor ran brown with molasses for roughly six months after January 15, 1919. North End residents reported the sweet smell rising from sidewalks and basements on warm days for decades. Journalist Edwards Park described the scent as part of the neighborhood’s identity well into the late twentieth century.

Who was held responsible for the molasses flood?

United States Industrial Alcohol Company (USIA), parent of Purity Distilling, was found fully liable in April 1925. Court-appointed auditor Colonel Hugh W. Ogden ruled that USIA’s negligent tank construction — not Italian anarchists, as the company claimed — caused the disaster. USIA paid roughly $1 million in initial damages, with later settlements estimated near $7 million.

Where was the molasses tank located in Boston?

The tank stood at 529 Commercial Street in Boston’s North End, near the Boston Harbor waterfront and at the foot of Copp’s Hill. Today the site is Langone Park and Puopolo Park, where a small plaque placed by the Bostonian Society commemorates the disaster. The Charlestown Bridge and Hanover Street remain nearby landmarks.

How big was the molasses flood plaque, and where can I find it?

The Boston Molasses Flood plaque is a small bronze marker placed by the Bostonian Society at the entrance to Puopolo Park, on Commercial Street near North End Park. It briefly summarizes the date, location, and 21 deaths. Visitors often miss it because the marker is modest and unobtrusive, set against the park railing.

Why was so much molasses stored in downtown Boston?

Boston was a historic center for the molasses-rum-alcohol trade dating to the colonial Triangular Trade. By 1915, USIA used Caribbean molasses to manufacture industrial alcohol for World War I munitions like cordite. With Prohibition approaching in 1920, the company also raced to distill rum before the ban took effect, driving Purity Distilling’s around-the-clock production schedule.